Temporal and spatial distribution of dengue in an urban setting: evidence from Hanoi, Vietnam (2018-2022).

Dengue fever remains a major mosquito-borne disease in Southeast Asia, with increasing incidence in rapidly urbanizing settings. In Vietnam, Hanoi has experienced recurrent outbreaks; however, comprehensive analyses of recent dengue epidemiology in northern regions remain limited. This study aimed to characterize the spatiotemporal dynamics of dengue in Hanoi from 2018 to 2022. A retrospective descriptive study was conducted using routine dengue surveillance data collected by the Hanoi Center for Disease Control. All clinically diagnosed and laboratory-confirmed dengue cases reported between January 2018 and December 2022 were included. Temporal trends were examined using descriptive analysis of monthly and annual incidence rates. District-level incidence rates were calculated and visualized using a geographic information system (GIS) mapping. Serotype distribution was examined using available virological data. A total of 46,650 dengue cases were reported during the study period. Dengue transmission occurred annually, with substantial inter-annual variability; the highest incidence was recorded in 2022 (236 per 100,000 population), while the lowest occurred in 2021 (41 per 100,000 population). A clear seasonal pattern was observed, with cases increasing from June and peaking between September and November. Spatial analysis revealed marked heterogeneity, with higher incidence consistently observed in peri-urban districts. All four dengue virus serotypes co-circulated, with DENV-1 and DENV-2 predominating and a shift toward DENV-2 dominance in later years. Dengue transmission in Hanoi exhibits pronounced seasonal and spatial patterns influenced by urbanization and ecological factors. Strengthening pre-season vector control activities and district-level surveillance may help reduce outbreak risk and maintaining integrated epidemiological and virological surveillance is essential to mitigate future outbreaks.